SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42f9a886f2d1a2575ea4fe68c52d45769b306a2e7dd2a046ff8abdc58e3bc3a8' 
  AND token = 'sFA9s+upxo+62aKU0uFMDF/ErWA9j35y0XmzTm56JMI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}